Tear-away sheath introducers (“sheath introducers” or “introducers”) and their use as medical devices are well known in the art. See, for example U.S. Pat. Nos. 6,814,718, 6,808,520, 6,808,509, 6,796,991, 6,740,101, 6,712,791, 6,712,789, 6,695,810, 6,641,564, 6,632,234, 6,623,460, 6,599,302, 6,361,559, and 5,558,652, as well as U.S. Patent Applications Nos. 20040260243, 20040254534, 20040176781, 2004006330, 2004097863, and 2002072789, the disclosures of which are incorporated herein by reference. These introducers are used in medical procedures to insert a catheter into the body and provide vascular access to the vessel of a patient. The catheters are inserted via the introducers by first using a needle to create an access site. A dilator is then used to dilate the access site to allow a larger-diameter sheath introducer to be introduced into the vessel through the access site. The catheter is then inserted through the sheath introducer and into the vessel. After the catheter has been inserted, the sheath introducer is removed, leaving the catheter in the vessel.
As shown in FIG. 19, conventional tear-away (or split) sheath introducers 100 usually contain four major components: (1) a dilator 140; (2) a tear-away sheath hub 110; (3) a tear-away valve 120; and (4) a tear-away sheath 130. The dilator 140 facilitates insertion of the sheath introducer 100 into the vascular system and maintains the inside diameter of the sheath 130 during insertion. The dilator 140 is normally locked into the hub 110 in order to keep it seated within the sheath 130. The dilator 140 typically contains a tapered tip 142 to facilitate insertion into the vascular system with the other end 144 of the dilator containing a standard medical luer hub 146. Both the distal end 142 and the proximal end 144 of the dilator 140 are usually manufactured of a rigid polymer.
The tear-away hub 110 provides a means to contain the valve 120 while connecting the valve 120 and the sheath 130. The hub 110 typically has a “T” shape with the opposing ends of the “T” being grasped and pulled to split both the valve 120 and sheath 130. Thus, the hub 110 provides a mechanism to split the sheath 130 into two portions and allow the introducer to be split and removed from around the catheter. The hub 110 is also often manufactured of a rigid polymer.
The tear-away valve 120, however, is typically made of a flexible material (such as silicone) that provides a self-sealing slit. The valve 120 may be designed as one piece that tears in half during the splitting procedure, or as two (or more) pieces that separate from each other during the splitting procedure. With conventional introducers, the valve 120 is encapsulated by the hub 110.
The tear-away sheath 130 is normally manufactured as a thin-walled structure, often as an extrusion. The extrusion contains splitting means, i.e., score lines that facilitate splitting or a self-splitting propagating material (such as linearly-directional extrusion). The proximal end 132 of the sheath 130 is attached to the hub 110 using over-molding or any other known attachment mechanism. The distal end 134 of the sheath 130 can be tapered to provide a smooth transition at the dilator/sheath interface.
To use the introducer 100, it is inserted in the desired vessel. Then the dilator 140 is unlocked from the hub 110 and removed to allow room for a catheter (or any similar medical device) to be inserted into the sheath. The valve 120 remains stationary inside the hub 110 and blocks air and/or fluid from flowing through the sheath 130 and hub 110 when they are left behind after the dilator is removed. The valve 120 keeps the passage 105 clear until a catheter is inserted into the passage 105 through the valve.
The introducer 100 is typically used for larger catheters, i.e., those with a diameter of 12 to 16 French. These larger-diameter introducers are rigid due to their diameter and the material used to construct them. This rigidity allows the large catheters to overcome the frictional forces needed to push the catheter through the valve.
But inserting smaller catheters into smaller introducers is more difficult. Typical introducers designed for smaller catheters (i.e., those 3 to 12 French in diameter) are made with open communication between the access site and the vascular system once the dilator is removed. This open configuration exists because smaller catheters, due to their smaller diameter and material, are not rigid enough to overcome the frictional forces needed to push the catheter through the valve. In other words, it is like trying to “push” a rope through a hole: the rope (i.e., catheter) does not remain rigid enough for a user to push it through the hole (i.e., valve).
The open configuration between the vascular system and the environment, however, allows two serious clinical problems. First, air embolism into the vascular system which can result in patient injury and/or death. And second, release of potentially infectious bodily fluids (including blood) into the environment, resulting in exposure to the health care provider.